Life slowly returns to poisoned seafloor

By Bill Cummings

Updated 11:11 am, Sunday, December 27, 2015

An illegal pile of contaminated dredge spoils — the worst possible sediment — lies deep under the water six miles off New Haven.

The sticky silt from Black Rock Harbor in Bridgeport contains a toxic slurry of cancer-causing compounds such as polychlorinated biphenyls (PCBs) and polynuclear aromatic hydrocarbons (PAHs), along with dangerous heavy metals such as chromium and copper.

The 73,000 cubic yards of material, more than the volume of cement in the Empire State Building, was deposited there by the U.S. Army Corps of Engineers in 1983 to test what would happen to the surrounding ecosystem if highly noxious polluted material was introduced.

“It would not be possible to repeat it,” said Drew Carey, a Rhode Island marine scientist who often works for the Army Corps. “The idea was, ‘Let’s take what would fail the test.’ ”

In fact, anyone who now dumped a similar mound of dredge spoils at the central Long Island open water disposal site would be arrested and jailed.

That type of material, both then and now, must be buried within a harbor and tightly capped. The cap is fashioned from clean sediment taken from the harbor or nearby and tightly packed over the hole so the contaminated material cannot escape.

The other dredged material at the site — some 14 million cubic yards — is contaminated but within acceptable thresholds established by the federal Environmental Protection Agency.

Life in extreme

Marine life initially did not thrive at the site — but it did not entirely stay away from the toxic mound, according to Army Corps and scientists who have studied mound for more than 30 years.

Some of the area was reclaimed by small aquatic creatures and plants which live nearby, while other parts remain barren.

“Initially, the mound did not recolonize very well,” Drew said, referring to the process of marine life burrowing and occupying a new feature on the bottom of the Sound.

“Later, it was not fully developed,” Carey said. “In some areas, it did rather well. Some of it looks just like it did in 1985.

“But it’s not dead,” Carey said of the underwater region. “It’s less recovered than others. It’s not devastating to the bottom of Long Island Sound. It did not kill that part of Long Island Sound.”

The point of the experiment, said Army Corps officials, was to “field-verify existing test methods for predicting the environmental consequences of dredged material disposal under aquatic, wetland and upland conditions” at an unconfined open-water disposal site.

Black Rock sediment

The Corps, in a recent monitoring report of the site, noted prior to dredging the material that “exposure to the Black Rock Harbor sediments resulted in both chronic and acute effects in several test species, as well as PAH and PCB bio-accumulation.”

“The underlying assumption of the Field Verification Program was that if adverse effects were to be seen from placing sediment with elevated contaminant concentrations on the seafloor, they should occur on this particular mound,” the Army Corps explained.

The Corps said testing of the site determined the material caused no lasting harm to the Sound.